A functional developer roller for use in contact electrophotographic printing having a high resistance surface layer over a semi-conductive core gives excellent print performance independent of the speed of movement of the printing members (termed process speed). This is an improvement over a more common method which involves making a semi-conductive core and subsequently coating that core with a resistive material in a separate process such as spray or dip coating.
By using the novel combination of materials described in the foregoing Ser. No. 08/629,855, a high resistance surface layer over a more conductive core can be produced simply by oxidizing the roll surface. This eliminates the need for coating the conductive roll with a resistive layer in a separate process. This process is an improvement over a more common method which involves making a semi-conductive core and then subsequently coating the core with a resistive material in a separate process such as spray or dip coating. Baking is much more cost effective than spray or dip coating and produces a roller with less defects. The baked polydiene-based roll of this invention mimics the electrical performance of the coated roller and gives excellent print performance over a wide range of process speeds.
However, during the functional life of the roller, that material set is susceptible to further oxidation, also known as aging or oxidative aging, which may have a deleterious effect on the properties of the roller.